ARP table shows incomplete entry and connectivity lost

I have Linux device running 4.14.7 kernel. My device-A is directly connected to third-party device(Device-B) over 1Gig port. A UDHCPD server runs on dev-A which always assigns single IP address as per DHCP config. Dev-A is in 172.16.x.x with mask 255.255.0.0. Dev-B is assigned with 172.16.100.1 with 255.255.255.0 from UDHCPD running on Dev-A. Occasionally I see that "arp" table is showing "incomplete" for Dev-B and communication fails. At this time I can see that Dev-B has valid lease from UDHCPD server.

$arp
?                (172.16.100.1) at                                            on      br0

A ping will restore the connection to Dev-B. How do I overcome this issue without issuing a "ping"? Thanks in advance.